The present invention relates to surgical instruments, particularly, to a surgical instrument for performing intervertebral surgery for stabilizing the spine.
A common medical condition is chronic low back pain due to spinal disc problems. Low back pain is the most frequent cause of disability in persons under age 45 years, and the third most frequent cause in the 45-64 age group. Currently, there are 2.6 million Americans temporarily disabled and another 2.6 million Americans permanently disabled by chronic low back pain. Approximately 2 percent of all workers injure their back annually.
The need to rehabilitate these patients quickly and return them to a productive life style is obvious as studies indicate the ability to ever work again decays rapidly after six months. If an injured worker has not returned to work within two years, chances are very high that he or she will never work again.
Low back pain can be avoided if relative motion between spinal vertebra can be prevented. Intervertebral stabilization is sought in a variety of treatment methods. To abate low back pain, stabilization is directed to stabilizing contiguous vertebra in the lumbar region of the spine. A common non-surgical procedures is the use of back braces. The brace is worn externally by the patient to restrict lumbar movement. The brace however is bulky and uncomfortable and limited in its effectiveness.
Laminotomy with discectomy is the standard treatment for patients with disc protrusion producing sciatica. The procedure is performed under general anesthesia. A surgical incision is made and the surgeon directly visualizes the posterior disc and nerve root. The disc extrusion or free fragments are excised and removed. However, this direct approach necessitates entry into the spinal canal, thereby putting the patient at risk for epidural bleeding, perineural fibrosis and reherniation from the site of the annular fenestration.
Low back pain is associated with the degeneration of the intervertebral disc which commonly occurs with age. Surgical stabilization seeks to rigidly join the lumbar vertebra which are separated by the degenerated disc. Ideally, the surgery effectively replaces the vertebra-disc-vertebra combination with a single rigid vertebra. That is, adjacent vertebra are fused together to form a single vertebra.
Various surgical techniques have been developed for alleviating lower back pain. One surgical approach is directed to a total disc removal through a partial hemilaminectomy. This is a major surgical procedure; it is costly and the in-hospital convalescence is long.
Another procedure, chemonucleolysis, has been developed to avoid the problems associated with major surgery. The intradiscal pressure is decreased by the percutaneous introduction of chymopapain entered into the intravertebral disc to dissolve it. Such an approach is effective in the majority of patients but does have some side effects, as some patients are hypersensitive to the drug.
Arthroscopic discectomy offers an alternative method treatment for lumbar radiculopathy due to herniated disc. Several such devices are described in U.S. Pat. No. 4,203,444; 4,598,710; 4,603,694; 4,834,729; and 5,062,845. However, none of these devices are without limitations such as the time consuming removal of very small amounts of tissue via the guillotine cutting approach, the clogging of cutters and cannula due to adherent tissue fragments and, with the use of lasers, very slow canalization of the nucleus pulposus, time consuming ablation with considerable heat and char at the operative site.
Recent clinical studies have shown that patients can benefit from minimal invasive surgery utilizing the percutaneous approach. Removal of nucleus pulposus from lumbar disc, utilizing small cannula and cannulated surgical instruments, with or without endoscopic aids, thereby reducing surgical trauma, can result in immediate relief of symptoms, low morbidity and cost efficiencies.
It is therefore an object of the present invention to provide a surgical instrument for removing all or part of a intervertebrate disc employing a minimal invasive surgical technique.
It is another object of the present invention to provide a surgical instrument that eliminates all of the aforesaid problems, does not compromise future surgical procedures and offers a number of advantages including: avoidance of epidural bleeding and perineural fibrosis, elimination of reherniation through intraoperatively induced annular fenestration, preservation of spinal stability, and the establishment of a portal space for fusion.